1. Field of the Invention
The present invention relates to a control device for an internal combustion engine, and, more particularly to a control device for an internal combustion engine that suppresses heat generation of a driving circuit of an injector.
2. Background Art
An injector that injects fuel into an internal combustion engine injects the fuel with an electric current from an injector drive circuit applied thereto. However, when energization time and the number of times of energization for the injector increase, power consumption of the injector drive circuit increases. As a result, a control device including the injector drive circuit generates heat.
In particular, in the case of a cylinder injection internal combustion engine, the pressure of fuel that should be injected has to be set high. Therefore, the injector drive circuit includes a circuit for boosting the voltage from a battery. The injector drive circuit has to energize the injector with the voltage boosted by using the circuit. As a result, an electric current flowing to the injector drive circuit is large compared with that in the past. The injector drive circuit more easily generates heat and tends to break down, which is likely to lead to the failure of the control device.
In order to prevent the failure of the control device due to the heat generation, a temperature detection device that detects the temperature of the injector drive circuit is provided. When it is judged that the detected temperature exceeds predetermined temperature (shutdown temperature) and is excess temperature, the normal control of the internal combustion engine is stopped and the driving of the injector drive circuit is stopped (shut down). When the detected temperature falls to be equal to or lower than the predetermined temperature, the shutdown is released and the normal control is resumed.
However, even if such a measure is taken, when the detected temperature does not exceeds the shutdown temperature and the normal control is continuously performed near the shutdown temperature, a temperature rise due to the heat generation of the injector drive circuit is accelerative. As a result, the temperature of the injector drive circuit easily exceeds the shutdown temperature and an engine of a vehicle is stopped.
In view of such a point, a control device for an internal combustion engine disclosed in JP Patent Publication (Kokai) No. 2005-201091 (Patent Document 1) performs control to inject fuel plural times in one combustion stroke. When temperature detected from an injector drive circuit exceeds predetermined temperature equal to or lower than maximum operation guarantee temperature of the injector drive circuit, the control device performs, according to the excess temperature, control for driving an injector via the injector drive circuit to reduce the number of times of injection of the fuel per one stroke. With such a control device, it is possible to suppress the heat generation of the injector drive circuit and keep the temperature of the injector drive circuit within a range of operation guarantee temperature by reducing the number of times of fuel injection.